The present invention relates to a construction of a power train system comprising an internal combustion engine (hereinafter referred to as an engine), an electric power device (hereinafter referred to as a motor) and a power transmission apparatus, and particularly to a power transmission apparatus adapted to enhance the transmission efficiency of the power train system.
Japanese Patent Laid-Open No. Hei 8-98322 discloses a known example using a power transmission apparatus adapted to enhance the transmission efficiency of the power train system.
In the above publication, there is described a power train construction in which an engine and a generator are connected to each other through a speed increasing gear, and a torque from an output shaft of the generator is transmitted to a motor through a clutch. In the above-described power train construction, since the generator and the motor permit high accuracy adjustment of the number of revolutions of the output shaft, torque variation at the time of switching between a series mode and a parallel mode (series mode: running by only the motor using energy generated by the engine; parallel mode: running by the engine and the motor) caused by engagement and disengagement of the clutch can be suppressed.
It is necessary for the above-described system to synthetically control the engine, the motor and the generator so that an operator (a driver) may operate the engine and the motor in a high efficiency region while satisfying acceleration and deceleration required by an operator. Therefore, a constitution is provided in which the engine is connected to the generator, and a torque from the output shaft of the generator is transmitted to the motor through the clutch.
With this constitution, in the case where the vehicle is intended to be accelerated in the state in which the clutch is engaged (the parallel mode), an inertia torque of a generator rotating portion occurs, and it is necessary to correct a torque corresponding to the inertia torque by the engine or the motor. Thus, it is impossible to avoid an increase in fuel consumption due to the inertia torque.
In view of the foregoing, it is an object of the present invention, in the case where the aforementioned parallel mode operation is employed and charging of a battery is not necessary, to suppress the generation of the inertia torque thereby improving fuel economy of the vehicle.
For achieving the aforementioned object, there is provided a power transmission apparatus for an automobile comprising an engine, a generator driven by an output of the engine, a battery charged by a generation output of the generator, and a motor driven by a discharge output of the battery, wherein a clutch mechanism is provided between an output shaft of the engine and an output shaft of the generator.
Preferably, the clutch mechanism is a device which requires no energy for engagement and disengagement when it is engaged or disengaged.
Preferably, the clutch of the clutch mechanism is a dog clutch.
Preferably, there is used a clutch mechanism using a linear actuator (e.g. a motor, a gear and a rack) for driving the dog clutch.